1. Field of the Invention
The present invention relates to a camera capable of reading/writing information of a photo film cassette. More particularly, the present invention relates to a camera capable of reliably detecting existence of a photo film cassette by utilizing reading of information of the photo film cassette.
2. Description Related to the Prior Art
A photo film cassette of a widely used 35 mm type includes a spool rotatably contained in a cassette shell, and a silver salt photo film wound about the spool in a roll form and contained in the cassette shell. Outside the cassette shell, there are a bar code printed to represent information including photo film speed, and numerals or signs printed to indicate the maximum number of available frames of the photo film. A photo film passage port or slit is formed along the cassette shell, and adapted to passage of the photo film for unwinding and winding back. In the 35 mm type, a DX code is used to represent the information.
After development of the photo film, the cassette shell of the 35 mm photo film cassette is discarded as a waste. The photo film is cut into pieces each of which includes a predetermined number of frames. Those photo film pieces are inserted into a sheet holder or photo film sheaths. The photo film being developed is handled by a photofinisher to produce photographic prints or photographs by exposing photographic paper with frames recorded on the photo film.
There is also a new standardized photo film cassette known as IX240 type, which includes the photo film, the spool and the cassette shell being plastic. The cassette shell has a photo film port shutter or cassette shutter disposed in a rotatable manner between open and closed positions in a photo film passage port. When the spool is rotated in a direction to unwind the photo film, a leader of the photo film is advanced from the inside to the outside of the cassette shell through the passage port being open.
The spool further includes a data disk and a status indicator mechanism, both of which are rotatable integrally with a core of the spool, and are visible through openings or holes formed in the cassette shell of the new standardized photo film cassette.
On the data disk is disposed a rotary bar code, which represents photo film information including photo film speed or ISO sensitivity, the maximum number of available frames of the photo film, and a photo film type. When a camera is loaded with the new standardized photo film cassette, a photo sensor automatically reads the data disk to recognize the information. The indicator mechanism includes four indicia holes and an indicator tongue. An end face of the cassette shell has the four indicia holes formed through it in different shapes. The four indicia holes represent an unexposed status, an exposed status, a developed status, and a partially exposed status. The indicator tongue is disposed fixedly with an end of the spool, and stopped behind one of the indicia holes, to indicate one of four statuses of the photo film.
The user is enabled to use the new standardized photo film cassette with the camera to take photographs in such a convenient manner as the 35 mm photo film cassette. The new standardized photo film cassette has an additional feature of containing the roll of the photo film after development for preservation. The cassette shell of the new standardized photo film cassette can be effective when the new standardized photo film cassette is loaded in various external optical instruments. Visible images of the photo film being developed can be electrically reproduced on a monitor display or printed on a sheet. The new standardized photo film cassette is useful as a container for the recording medium by the virtue of its compatibility to an audio-visual system.
The new standardized photo film cassette being standardized newly is different in the structure and operation from the 35 mm photo film cassette. Even if a user erroneously loads the newly standardized camera with the 35 mm photo film cassette, the 35 mm photo film cassette is automatically treated in the camera without recognizing the error, to damage both the 35 mm photo film cassette and the camera. Even after the erroneously inserted cassette is unloaded from the camera, an accidental operation is likely to occur when the new standardized photo film cassette is acceptably inserted in the camera.